There is roll-bending processing as a method for carrying out bending processing of a thin plate or a wire rod. This is processing that acts bending stress on a material to be processed and bends the material, by controlling a feeding amount of the material to be processed fed to a processing part configured of at least three rolls and a position of at least one roll of the processing part. In the processing method, an arbitrary curvature can be imparted to a material to be processed without using a die, and thus there is an advantage that the cost is lower than that of bending by press.
However, when a material to be processed is made of a metal, springback is generated by removal of the bending stress and a radius of curvature is changed. When a radius of curvature of a design shape is constant, processing can be carried out comparatively easily by appropriately adjusting the position of a pushing roll. However, in a case of a design shape in which a radius of curvature is changed, setting of the pushing roll position becomes very difficult. There are Patent Literatures 1 to 3 as conventional technologies of bending using rolls.
In Patent Literature 1, there is disclosed a technology about a bending processing method of a steel plate or the like. Specifically, a cam of a similar figure to a design shape is rotated in synchronization with rotation of a supply roll, and at the same time, a displacement magnitude of a follower paired with the cam is converted to an electric quantity, and an elevation amount of a pushing roll is controlled via a hydraulic servo or the like, and thus a curved plate, a pipe or a tubular body is automatically formed.
In Patent Literature 2, there is disclosed a technology about a bending processing method of a metal material by a bending roll and a device thereof. Specifically, there is disclosed a method in which bending processing is experimentally carried out in advance and average value data of springback ratios are collected and stored in a memory, and an intended springback ratio is obtained by the use of the data at an intended processing radius, and in which processing conditions considering springback are found from the springback ratio.
In Patent Literature 3, there are disclosed technologies concerning a roll bending method and device. Specifically, there is disclosed a processing method in which, in pinch-shape roll bending, a position of a pushing roll at which the pushing roll makes contact with a material to be processed is calculated from a geometric relationship between a roll arrangement and a processing shape, and in which push-in amount for imparting a curvature is derived from elasto-plasticity simulation by a finite element method or the like until the calculated position of the pushing roll falls within the allowable deviation.
In Non Patent Literature 1, there is disclosed a technology concerning bending processing in a modified shape by pyramid-shaped three rolls based on Non Patent Literature 2. Specifically, in the pyramid-shaped three rolls, variously different bending shapes are automatically processed by numerically controlling a feeding amount of a material to be processed and the position of the central roll. In deriving the roll position, the processing by the use of roll press bending is started, and thus a subsequent wire rod shape between rolls is obtained by carrying out sequential calculation from the relationship between push-in amount and moment, with the result that the position of the roll for carrying out processing into an intended shape is determined.